A cascade of bHLH-regulated pathways programs maize anther development
A cascade of bHLH-regulated pathways programs maize anther development
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DOI：
10.1093/plcell/koac007
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发表时间：
2022-01-17
期刊：
影响因子：
11.6
通讯作者：
Walbot, Virginia
中科院分区：
文献类型：
--
作者：
Nan, Guo-Ling;Teng, Chong;Walbot, Virginia
花药瓣体组织的时空发育是成功产生可育花粉的必要条件。这一过程是由许多转录因子通过复杂的、多层的网络介导的。在此，我们对玉米（Zea mays）中相互作用的基本螺旋-环-螺旋基因Ms23、Ms32、基本螺旋-环-螺旋122 （bHLH122）和bHLH51的功能敲除突变体进行了分析，发现雄性生殖能力需要这四个基因在绒绒层（TP）中依次表达。它们不仅相互调节，而且还编码形成异源二聚体的蛋白质，这些蛋白质协同作用，指导特定发育阶段的许多细胞过程。MS23被证实是主控因子，因为MS23突变体在TP中表现出最早的发育缺陷，细胞学上可见，在MS23花药中观察到的减数分裂前基因表达的变化最为剧烈。值得注意的是，雄性不育的ms23、ms32和bhlh122-1突变体缺乏24-nt期次级小干扰RNA （phasiRNAs）和相应的24-PHAS位点的前体转录物，而bhlh51-1突变体具有野生型的前体和小RNA产物水平。多种证据表明，24-nt phasiRNA的生物发生主要发生在MS23和MS32的下游，两者都直接激活Dc15，并且是大多数24-PHAS转录所必需的，bHLH122在24-PHAS转录中起着明显的作用。
The spatiotemporal development of somatic tissues of the anther lobe is necessary for successful fertile pollen production. This process is mediated by many transcription factors acting through complex, multi-layered networks. Here, our analysis of functional knockout mutants of interacting basic helix-loop-helix genes Ms23, Ms32, basic helix-loop-helix 122 (bHLH122), and bHLH51 in maize (Zea mays) established that male fertility requires all four genes, expressed sequentially in the tapetum (TP). Not only do they regulate each other, but also they encode proteins that form heterodimers that act collaboratively to guide many cellular processes at specific developmental stages. MS23 is confirmed to be the master factor, as the ms23 mutant showed the earliest developmental defect, cytologically visible in the TP, with the most drastic alterations in premeiotic gene expression observed in ms23 anthers. Notably, the male-sterile ms23, ms32, and bhlh122-1 mutants lack 24-nt phased secondary small interfering RNAs (phasiRNAs) and the precursor transcripts from the corresponding 24-PHAS loci, while the bhlh51-1 mutant has wild-type levels of both precursors and small RNA products. Multiple lines of evidence suggest that 24-nt phasiRNA biogenesis primarily occurs downstream of MS23 and MS32, both of which directly activate Dc15 and are required for most 24-PHAS transcription, with bHLH122 playing a distinct role in 24-PHAS transcription.